Some of the world’s largest corporations were housed in the WTC. What was the impact of 9/11 to a) the economy of these corporations, b) the economy of the US? Any of them forced to go out of business because of 9/11? Are there any studies on the subject?
I am no economic theorist but I’ll tell you something from my limited point of view: charities and not-for-profits.
2001-2002 were our worst years ever. People did not want to open their pockets. As a matter of fact, this is the first year we’ve made budget since. (We came close last year). Since 9/11, we’ve been cutting services like crazy to try and keep up with the downward spiral. It’s been hurting us badly.
The Not For Profit Times ran a series of articles on this phenomenon. (Ok, which one is plural, and which one is singular: phenomena? I better go join those intellectually inferior Dopers!)
“Phenomenon” is the one you want. “Phenomena” is plural. Now if only I could be sure that I spelled them correctly. 
Doot doooo dah doo doo!
Lots of good info here: http://www.gao.gov/new.items/d02700r.pdf